Boat hulls for planing watercraft encounter a wide variety of water surface conditions over which the hull must provide safe transport. Typical surface conditions range from flat, smooth surfaces associated with protected bays and inlets to choppy waves found in open bays to smooth or choppy swells encountered in offshore ocean areas. Hulls designed to provide safe and comfortable carriage under one set of sea conditions may be unsafe and uncomfortable when used under conditions different from those for which the hull was primarily designed.
The most popular hull design for power boats traveling on a plane is a V configuration. The V configuration represents a compromise between lateral stability, such as may be achieved with a catamaran or flat bottom design, and the need to avoid excessive bouncing or "pounding" that occurs when a flat or rounded bottom is propelled at planing speeds over a moderately choppy water surface. One weakness of most designs is that, as the speed of the hull increases, a wide forward configuration may tend to act as an airfoil, causing the hull generate excessive lift in the forward portion that sometimes produces the up and down motion commonly known as "porpoising." This phenomenon is exacerbated in rough or choppy water in which the hull may be given an initial upward lift by a wave or swell, may be further lifted by the aerodynamic force of the air and, after reaching a maximum height, will fall back to the surface to crash against the next wave. Such pounding is not only uncomfortable to passengers, but places undue stress upon structural components within the boat and can be dangerous.
Where high speed operation is desired, a deepening and narrowing of the V configuration is helpful in reducing the aerodynamic tendency of the hull to act as an airfoil and become airborne over the water surface. The deep V also helps to part the water, resulting in a lessening of the pounding of the hull as it meets the water. A deep V having a 24.degree. dead rise at the transom permits a softer water entry when landing after leaving the water. These advantages may be increased by sharpening and lightening the forward entry area. These features may be found on nearly all modern ocean running high performance hulls.
Further deepening of the V will ameliorate the vertical motion of the forward part of the hull, providing greater longitudinal stability while continuing to reduce porpoising action. However, such benefits are gained at the expense of lateral stability, and the natural tendency of a deep V hull to rock and roll in moderate seas at slow speeds or while drifting places a practical limit upon the angle of the V that a hull may have without sacrificing comfort or safety.
In sharp contrast to deep V configurations are catamaran and flat bottom hull designs. Such designs may incorporate a right-angle hard chine at or near the water surface, and are exceptionally stable against lateral rolling. However, because they lack the features of a V or deep V configuration, they are not well suited for high speed rough water travel.